A watermarking system and method is proposed for still or moving pictures in which a watermark is embedded robustly and simply into DC-values, but without causing unacceptable visible picture degradation. The watermark is secure and can be readily detected, and the method can be used to convey additional data. Also disclosed is a method for watermarking a sequence of pictures in which the visibility of artifacts is reduced. The watermark may carry data and may be used to label a program.
Legal claims defining the scope of protection, as filed with the USPTO.
2. A method according to claim 1 , wherein said number of substantially independent watermarks comprises a subset selected from a defined set of substantially independent watermarks.
3. A method according to claim 2 , wherein said number is three.
4. A method according to claim 2 , wherein there are more than three substantially independent watermarks in said set.
5. A method according to claim 1 , wherein the subset is selected or said substantially independent watermarks are selected in dependence on information to be encoded in the picture.
6. A method according to claim 1 , wherein three bipolar watermarks are combined to produce a single bipolar watermark with the property that the product of the combined watermark with each of the constituent marks has an expectation value of ½.
7. A method according claim 1 including generating the watermark by convolving a key with a repeated data sequence to produce a data-carrying watermark.
8. A method according to claim 1 , wherein the picture is divided into two or more sub-pictures, and a substantially independent watermark is embedded into each sub-picture.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
March 20, 2000
October 31, 2006
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